1. Field of the Invention
The present invention relates to a tire pressure indicator and, more particularly, to a diaphragm-type tire pressure indicator.
2. Description of Related Art
Conventionally, a tire pressure indicator is provided for warning insufficient tire pressure, thereby ensuring the safety in driving a vehicle. In such an indicating device, a flexible piston device is generally used to move forwards/backwards subject to the condition of the tire pressure of a vehicle tire, so as to sense the pressure of the tire and thus detect whether the pressure is too low. This conventional tire pressure indicator produces only a small friction during movement of the piston, and the tire pressure indication is relatively accurate.
U.S. Pat. No. 5,677,492 granted to the present inventor discloses a diaphragm-type pressure measuring device, which uses a diaphragm to detect the tire pressure of the vehicle tire. Similar tire pressure indicators are disclosed in U.S. Pat. Nos. 4,945,337, 5,014,643, 5,025,244, 5,289,161, and 5,694,111, for monitoring the tire pressure condition of vehicle tires. These tire pressure indicators are designed subject to different manners in warning low tire pressures. Therefore, based on different tire pressure warning requirements, various tire pressure warning devices, which are different in structures and are assembled in different manners, must be manufactured. As a result, the manufacturing process cannot be simplified and the manufacturing cost is high. Therefore, it is desired for the above conventional tire pressure indicators to be improved, so as to mitigate and/or obviate the aforementioned problems.
It is one object of the present invention to have a diaphragm-type tire pressure indicator, which has a simple structure and, can be applied to different tire pressure warning manners.
It is another object of the present invention to have a diaphragm-type tire pressure indicator, which has the function of micro-calibration and, is suitable for mass production.
In accordance with one aspect of the present invention, there is provided a diaphragm-type tire pressure indicator for being installed in the air nozzle of a vehicle tire to give an indication when the tire pressure of the vehicle tire is low. The diaphragm-type tire pressure indicator comprises a casing having a receiving chamber and a coupling unit; a flexible diaphragm mounted in the receiving chamber of the casing; a push rod connected to the flexible diaphragm for being moved up and down with the flexible diaphragm; a sleeve mounted in the receiving chamber of the casing and around the push rod, the sleeve having a bottom end and a top end; and a spring means sleeved onto the push rod.
In accordance with another aspect of the present invention, there is provided a diaphragm-type tire pressure indicator for being installed in the air nozzle of a vehicle tire to give an indication when the tire pressure of the vehicle tire is low. The diaphragm-type tire pressure indicator comprises a casing having a receiving chamber and a coupling unit; a movable diaphragm mounted in the receiving chamber of the casing; a push rod connected to the movable diaphragm for being moved up and down with the movable diaphragm; a sleeve mounted in the receiving chamber of the casing and around the push rod, the sleeve having a bottom end and a top end; an adjustment cap fastened to the top end of the sleeve in such a manner that the push rod extends out of the adjustment cap, so as to achieve a micro-calibration function by adjusting a position of the adjustment cap relative to the top end of the sleeve; a spring means sleeved onto the push rod; a conductive member mounted on the adjustment cap; a circuit board electrically mounted on the conductive member, the circuit board having a light emitting element; and a battery seat mounted on the push rod for holding a battery cell, the battery cell having a first electrode connected to the light emitting element and a second electrode electrically connected to the battery seat, wherein the battery seat is moved up and down with the push rod relative to the conductive member so as to selectively contact with the conductive member for turning on the light emitting element.
In accordance with a further aspect of the present invention, there is provided a diaphragm-type tire pressure indicator for being installed in the air nozzle of a vehicle tire to give an indication when the tire pressure of the vehicle tire is low. The diaphragm-type tire pressure indicator comprises a casing having a receiving chamber and a coupling unit; a movable diaphragm mounted in the receiving chamber of the casing; a push rod connected to the diaphragm for being moved up and down with the diaphragm; a sleeve mounted in the receiving chamber of the casing and around the push rod, the sleeve having a bottom end and a top end; an adjustment cap fastened to a top end of the sleeve in such a manner that the push rod extends out of the adjustment cap, so as to achieve a micro-calibration function by adjusting a position of the adjustment cap relative to the top end of the sleeve; a spring means sleeved onto the push rod; a conductive member mounted on the adjustment cap; a circuit board electrically mounted on the conductive member, the circuit board having an RF transmitter module; and a battery seat mounted on the push rod and for holding a battery cell, the battery cell having a first electrode connected to the RF transmitter module and a second electrode electrically connected to the battery seat, wherein the battery seat is moved up and down with the push rod relative to the conductive member so as to selectively contact with the conductive member for outputting a radio signal indicating a low pressure of the tire.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.